Little is known about the sleep of shift workers. This research project is examining the effects of shift work on the laboratory sleep of working-class men and women using electrophysiological and behavioral measures. Both EEG sleep-stage and averaged evoked brain response measures of sleep are being studied. Appropriate measurements of body temperature, mood, personality, vigilance performance, and off-the-job behavior are being made. The influence of job duties, work shift, sex of worker, and work shift history on these measurements is being examined to determine the relation of these factors to the health and safety of American workers.